Yes. It's the center of the board's ground potential for the circuit and PSU, and therefore the quiet spot for attaching the phono ground. It's not really mentioned in any of the literature, I know about it only through speaking with Wayne at Burning Amp.

Hopefully the center that I created on my prints (about the same spot) will have the same effect...

Replacing the Yamaha HT Receiver, using it as a Pre-Amp out to the F5 made a big difference. Most 'average' listeners would say my current rig sounds great. Compare to a digital source, and it is obvious there is room for improvement on the phono side. 6L6 and others have been polite in saying my Rega Bias 2 cartridge sucks compared to other choices. That may be a future bottleneck after I get the Pearl 2 going.

I also plan on building a B1 buffer pre-amp, it will be interesting to observe the improvements (hopefully) as I upgrade each element. I have Polk TSi300s, OK for the money - another candidate for an upgrade. Thinking a Troels TQWT if I can realistically find the time to build.

Have you lowered the gain for the Bias2 cartridge? I think its output is too high for the standard 55 dB gain (will give you almost 3V ouput). Time to save up for something like a Goldring Eroica

It's awfully hard to swamp the input of the Pearl. Just run the gain in the stock position. ...don't add any gain, obviously...

Yes, but the distortion at 5mV input is already around 0.25% according to the article by Wayne and the Bias2 has even more output. Expect between 0.3% and 0.35% distortion. But you won't destroy it, so just listen and decide if you're happy with it.